Method of cleaning CVD device

ABSTRACT

A method of cleaning a CVD vacuum vessel which has an electrically conductive partition plate which divides an interior of the vacuum vessel into a plasma generating space and a film-deposition processing space, and in the electrically conductive partition plate there is a plurality of through-holes connecting the plasma generating space to the film-deposition processing space, the method includes the steps of feeding a cleaning gas into the plasma-generating space; generating active seeds by applying high-frequency electric power to electrodes arranged in the plasma-generating space; feeding the generated active species into the film-deposition processing space through the plurality of through-holes in the electrically conductive partition plate; and cleaning the film-deposition processing space by the active seeds which have been fed into this film-deposition processing space.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the priority of Japanese PatentApplication No. 2001-012600, filed in Japan on Jan. 22, 2001, the entirecontents of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field of the Invention

[0003] The invention relates to a method of cleaning a chemical vapordeposition system(referred to in the present patent specification as“CVD system”).

[0004] 2. Description of Related Art

[0005] It is known to use high-temperature polysilicon-type TFTs(thin-film transistors) and low-temperature polysilicon-type TFTs inmethods of manufacturing liquid crystal displays.

[0006] In order to obtain high-quality oxide films in the manufacturingmethods using high-temperature polysilicon-type TFTs, quartz substrateswhich could withstand high temperatures of 1000° C. or more are used.

[0007] In contrast, in the manufacture of low-temperaturepolysilicon-type TFTs, it is necessary to carry out film deposition in alow-temperature environment (for example 450° C. or less) because aglass substrate which is customary for TFTs is used. Methods formanufacturing liquid crystal displays using low-temperaturepolysilicon-type TFTs have the advantage that they do not requirespecial substrates to be used. Such methods have been put into practicein recent years and their production volume is continuing to expand.

[0008] In the manufacture of liquid crystal displays usinglow-temperature polysilicon-type TFTs, plasma CVD is used when a siliconoxide film is deposited as a gate insulator film at low temperature.When silicon oxide film is deposited by plasma CVD, silane,tetraethoxysilane (TEOS) and the like are used as typical materials ingas form.

[0009] If silane, or the like, is used as the material in gas form andsilicon oxide film is deposited by means of plasma, in the conventionalplasma CVD system, silicon oxide film is deposited on the surface of asubstrate by introducing the material in gas form and oxygen, or thelike, into the space in front of said substrate, generating plasma in agas mixture comprising the material in gas form and the oxygen or thelike and exposing the substrate to said plasma.

[0010] The conventional plasma CVD systems are configured in such a waythat the material in gas form is supplied directly into the plasma whichis generated inside the plasma CVD system. For this reason, with theconfiguration of conventional plasma CVD system, there is a problem thatthe high-energy ions are injected from the plasma present in the spacein front of the substrate onto the film-depositing face of the substrateand they damage the silicon oxide film and degrade the properties of thefilm. Furthermore, as the material in gas form is fed directly into theplasma, particles are produced by violent reaction between the materialin gas form and the plasma, and as a result the yield is reduced.

[0011] In order to solve the above mentioned problems, an attempt toimprove the CVD device of the remote plasma type is disclosed in JapanPatent Application Serial Number H11-157692.

[0012] The CVD device disclosed in the above mentioned the patentapplication, Serial Number H11-157692, produces active seeds (radicals)by generating plasma inside a vacuum vessel, carries out thefilm-deposition processing on a substrate, accommodated inside saidvacuum vessel, by means of these active seeds and material in gas form.

[0013] That is to say, an electrically conductive partition plate whichdivides the interior of said vacuum vessel into two chambers is providedin said vacuum vessel. The interior of one of these two chambers isformed as a plasma-generating space in which high-frequency electrodeare arranged, and the interior of the other chamber is formed as afilm-deposition processing space in which a substrate-holding mechanismon which a substrate is mounted is arranged. A plurality ofthrough-holes which are made to pass from the plasma-generating space tothe film-deposition processing space are formed in this electricallyconductive partition plate. Furthermore, this electrically conductivepartition plate has an interior space which is divided off from theplasma-generating space and communicates with the film-depositionprocessing space via a plurality of diffusion holes. The system isconfigured in such a way that the material in gas form is supplied tothe interior space of this electrically conductive partition plate fromthe outside and fed into said film-deposition processing space throughsaid plurality of diffusion holes. The active seeds which are generatedin said plasma-generating space are fed into the film-depositionprocessing space through the plurality of through-holes formed in saidelectrically conductive partition plate and film processing is performedon said substrate in film-deposition processing space.

[0014] In said CVD system disclosed in Patent Application Serial NumberH11-57692, the plurality of through-holes which are made to pass fromsaid plasma-generating space and are provided in said electricallyconductive partition plate to said film-deposition processing space areformed to satisfy the condition uL/D>1 when the gas flow velocity insidesaid through-holes is u, the effective length of the through-holes is Land the coefficient of mutual gas diffusion is D.

[0015] As the plasma-generating space and film-deposition processingspace are separated by means of the electrically conductive partitionplate in said CVD system proposed in Patent Application Serial NumberH11-157692, the device is configured in such a way that the processingsurface of the substrate which is arranged in the film-depositionprocessing space is not exposed to the plasma. In addition, a pluralityof through-holes which are made to pass from the plasma-generating spaceto film-deposition processing space are formed in the electricallyconductive partition plate. However, because these through-holes areformed so as to satisfy the above_mentioned condition, the material ingas form which is fed into the film-deposition processing space isprevented from diffusing back into the plasma-generating space.

[0016] It is to be noted that in Patent Application Serial NumberH11-157692, a CVD system is proposed which is formed in such a way thatsaid plurality of diffusion holes also fulfill the above mentionedcondition placed on the through-holes, in order to prevent the activespecies fed into the film-deposition processing space from diffusingback into the interior space of the partition plate.

[0017] In fact, Patent Application Serial Number H11-157692 discloses aCVD system in which plasma is generated between the high-frequencyelectrode and the lower face part of the upper part of the vacuum vesseland in the space which is bounded by the high-frequency electrode andthe partition wall comprised of vacuum vessel which makes up the CVDsystem and the electrically conductive partition plate, both of whichare at ground potential. Further more, the variation of the abovementioned CVD system is disclosed in which, the high frequencyelectrodes are installed in upper positions in the plasma-generatingspace and plasma electrical discharge is produced between thehigh-frequency electrode and the electrically conductive partitionplate.

[0018] Generally, there are problems common to CVD systems that whenfilms continue to be deposited, they are also deposited on thesubstrate-supporting elements and the interior wall of thefilm-depositing chamber and the like. When they drop off onto thesubstrate during film deposition as particles, they cause to bedisconnect circuits of the wiring and result in the reduction of theyield of manufactures products.

[0019] For this reason, apart from the film-depositing process, optimumcleaning is carried out after processing the prescribed number ofsubstrates, said cleaning being performed using particular cleaninggases according to differences in the plasma-forming method andstructures and compositions of the deposited materials. The cleaning ofthis type of CVD device is an important process, as is thefilm-deposition process in the implementation of stabilized operation ofthe CVD system without exposing the interior of the depositing chamberto the atmospheric ambient.

OBJECTS AND SUMMARY

[0020] An object of the present invention is to provide an optimumcleaning process for the CVD system disclosed in Patent ApplicationSerial Number H11-157692.

[0021] In the manufacture of large liquid crystal displays in which lowtemperature polysilicon-type TFTs are used, the CVD device disclosed inPatent Application Serial Number H11-157692 uses plasma and depositssilicon oxide film on a large-area substrate using material in gas form,such as silane, in order to form at low temperatures a suitable siliconoxide film as a gate insulator film. An appropriate cleaning method isproposed which is suitable for this disclosed CVD system and a methodfor cleaning the CVD system is proposed in which the generation ofparticles is sufficiently suppressed, high manufacturing-product yieldby means of said CVD system is maintained and said CVD system_can carryout stable operations without exposing the interior of the depositingchamber to the atmospheric ambient.

[0022] A method of cleaning a CVD device according the present inventioncan be used in the CVD system disclosed in Patent Application SerialNumber H11-157692. According to one aspect of the present invention withan electrically conductive partition plate placed at ground potential,cleaning gas is fed into a plasma-generating space, active species aregenerated by applying high-frequency electric power to thehigh-frequency electrodes arranged in said plasma-generating space, saidgenerated active species are fed into a film-deposition processing spacethrough a plurality of through-holes in said electrically conductivepartition plate and said film-deposition processing space is cleaned bymeans of said active species fed into this film-deposition processingspace.

[0023] That is to say, in the CVD system which is disclosed in PatentApplication Serial Number H11-157692, the plasma-generating space andthe film-deposition processing space are separated from one another byan electrically conductive partition plate and a plurality ofthrough-holes is made to pass from the plasma-generating space to thefilm-deposition processing space in said electrically conductivepartition plate. The through-holes are formed such that they fulfilconditions which prevent back-diffusion to the plasma-generating spaceside of the material in gas form fed from the film-deposition processingspace.

[0024] Cleaning gas is fed directly into the plasma-generating space,which is separated from the film-deposition processing space by theelectrically conductive partition plate, and active species (radicals)are generated by applying high-frequency electric power to thehigh-frequency electrode inside said plasma-generating space. Thegenerated active species (radicals) are fed into the film-depositionprocessing space through the plurality of through-holes in theelectrically conductive partition plate, which is at ground potential,and the film-deposition processing space is cleaned by means of theactive species fed into the film-deposition processing space.

[0025] According to the present invention, it is possible to usefluoride gas as the cleaning gas. One or more types of the fluoridegases from such as, for example, NF3, F2, SF6, CF4, C2F6, C3F8 can beused.

[0026] When fluoride gas is used as the cleaning gas to apply thepresent invention to the actual cleaning, after processing of aprescribed number of silicon oxide films and a-Si films, fluoride gas isfed into the plasma-generating space, and active species (fluorineradicals) are generated by striking electrical discharge in theplasma-generating space. The fluorine radicals are fed into thefilm-deposition processing space through the plurality of through-holesin the electrically conductive partition plate at ground potential, andthe film-deposition processing space is cleaned. In other words,deposits attached to the inner walls of the vacuum vessel and to thesurface of the substrate-holding mechanism, and the like, react withsaid fluorine radicals and thus can be removed and expelled from anexhaust port.

[0027] In this respect, oxygen gas can be added to the above mentionedfluoride gas in order to further the dissociation into the fluorine atomradicals. For example, J. Appl. Phys. Vol. 52 (1981) p. 162 proposesthat by adding oxygen with a concentration of 60% or less, it ispossible to increase the density of fluorine atom radicals in comparisonwith cases in which there is no additive.

[0028] If fluoride gas is used, as mentioned above, the radicalsgenerated inside the plasma-generating space are fluoride radicals orfluorine atom radicals. However, but in cases where the deposits on thefilm-processing space and the like are carbonates, O2 is used as thecleaning gas.

[0029] In addition, in cases in which the density of the plasma is lowand a sufficient cleaning speed is not obtained, if an inert gas with ahigh ionization potential such as He, Ne, Ar, Kr and Xe is admixed withthe cleaning gas, it is possible to raise the temperature of theelectrons by the admixture of said inert gas, to further thedissociation of the cleaning gas such as fluoride gas and to increasethe cleaning speed.

[0030] In cases in which the method of cleaning a CVD system accordingto the present invention is implemented using fluoride gas as thecleaning gas as mentioned above, the cleaning gas which is adsorbed inthe inner face of the through-holes, in the partition plate and on thepartition plate during the cleaning step may desorb in the progress ofthe film-depositing step after the completion of the cleaning, may bedischarged into the film-deposition processing space from the interiorof the partition plate, and fluorine which is produced due to cleaninggas may be included in the thin film during the film deposition afterthe completion of the cleaning and degrades the intrinsic properties ofthe thin film.

[0031] The present application proposes a method of cleaning a CVDsystem which, as mentioned above, can suppress in advance theabove_mentioned problem which occurs in cases in which fluoride gas isused as the cleaning gas in the cleaning method according to the presentinvention.

[0032] In the method of cleaning the above_mentioned CVD system,according to one aspect of the present invention, when, with theelectrically conductive partition plate at ground potential, cleaninggas is fed into said plasma-generating space, active species aregenerated by applying high-frequency electric power to thehigh-frequency electrode arranged in the interior of saidplasma-generating space and said generated active species are fed intosaid film-deposition processing space through the plurality ofthrough-holes in said electrically conductive partition plate. Theelectrically conductive partition plate is heated, and morespecifically, heating of said electrically conductive partition platecan be carried out within a temperature range which suppresses theadsorption of fluorine onto the inner circumferential face of saidthrough-holes and the surface of the partition plate.

[0033] The temperature range at which the adsorption of fluorine ontothe inner circumferential face of the through-holes and the surface ofthe partition plate is prevented varies respectively depending on thetype of fluoride gas used as cleaning gas. For example, in cases inwhich the cleaning gas is a fluorocarbon gas such as CF4, C2F6, C3F8 andin cases when the cleaning gas is a nitrogen fluoride gas such as NF3the electrically conductive partition plate is heated to 200° C. ormore, and in cases when the cleaning gas is a fluorosulfur gas such asSF6 the electrically conductive partition plate is heated to 100° C. ormore.

[0034] Such heating of the electrically conductive partition plate canbe carried out, for example, by housing heating means, such as a heater,in the electrically conductive partition plate.

[0035] With the respective cleaning method, as it is possible to heatthe electrically conductive partition plate to the necessary temperatureat which the adsorption of cleaning gas onto the inner circumferentialface of said plurality of through-holes provided in said electricallyconductive partition plate and the surface of the partition plate isinhibitted, said heating being in accordance with the type of fluoridegas used as cleaning gas, it is possible to remove the fluorine which isabsorbed onto the inner circumferential face of the through-holes andthe surface of the partition plate during the cleaning and to prevent inadvance the fluorine contamination of the thin film during the filmdeposition of the film-depositing process after the completion ofcleaning.

BRIEF DESCRIPTION OF THE FIGURES

[0036]FIG. 1 is a view of a vertical section showing the configurationof a first embodiment of a CVD system in which the present invention canbe applied.

[0037]FIG. 2 is a view of a vertical section showing the configurationof a second embodiment in which the present invention can be applied.

[0038]FIG. 3(a) is an enlarged sectional view of places where thepartition plate is fixed.

[0039]FIG. 3(b)is an enlarged sectional view of an embodiment of thepartition plate in which heating means are housed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] An embodiment of a CVD system in which a cleaning methodaccording to the present invention can be applied will be described withreference to FIGS. 1 and 2.

[0041] The CVD device shown in FIGS. 1 and 2 are preferably used whensilane is employed as the material in gas form, and silicon oxide filmis formed as the gate insulator film on an upper surface of a glasssubstrate 11 which is customary for a TFT.

[0042] When film-deposition processing is carried out in the vacuumvessel 12, the vessel interior is maintained in a desired vacuum stateby means of an exhaust device 13. The exhaust device 13 is connected toan exhaust port 12 b-1 formed in the vacuum vessel 12.

[0043] In the interior of the vacuum vessel 12, a partition plate 14,which is made of electrically conductive material, is installed in ahorizontal state. The partition plate 14, which has a planar, forexample, rectangular, shape, is arranged in such a way that itsperipheral part forms a sealed state by pushing it down and attaching itto the lower face of the electrically conductive material fixing part22. In this way, the interior of the vacuum vessel 12 is separated intotwo chambers in the upward and downward directions by the partitionplate 14. The upper chamber is made into the plasma-generating space 15,and the lower chamber is made into the film-deposition processing space16.

[0044] The partition plate 14 has a desired specific thickness and isentirely in the shape of a flat plate. Furthermore, it is of planarshape similar to the shape of the horizontal section of the vacuumvessel 12. An interior space 24 is formed in the partition plate 14, anda plurality of through-holes 25 which fulfill specific conditions areformed and distributed throughout the interior space 24. Theplasma-generating space 15 and the film-deposition processing space 16communicate only via the through-holes 25.

[0045] A glass substrate 11 is arranged on a substrate-holding mechanism17 installed in the film-deposition processing space 16. The glasssubstrate 11 is essentially parallel with the partition plate 14 and isarranged in such a way that its film-depositing face (upper face) isfacing the lower face of the partition plate 14. The potential of thesubstrate-holding mechanism 17 is kept at ground potential 41 which isthe same potential as the vacuum vessel 12. Furthermore, a heater 18 isinstalled in the substrate-holding mechanism 17. This heater 18 is usedto keep the temperature of the glass substrate 11 at a prescribedtemperature.

[0046] The vacuum vessel 12 is configured, from the point of view ofimproving its assembly properties, of an upper vessel 12 a which formsthe plasma-generating space 15 and a lower vessel 21 b which forms thefilm-deposition processing space 16. When the vacuum vessel 12 is formedby assembling the upper vessel 12 a and lower vessel 12 b, theelectrically conductive partition plate 14 is installed between the two.In order to ensure that it is placed at ground potential, the partitionplate 14 is mounted so as to make contact with the electricallyconductive material fixing part 22, in the manner as shown in FIG. 3(a),for example. In this way, the separated plasma-generating space 15 andfilm-deposition processing space 16 are formed on the upper and lowersides of the partition plate 14 and the plasma-generating space 15 isformed by means of the partition plate 14 and upper vessel 12 a.

[0047] In the embodiment shown in FIG. 1, the region in which plasma 19is generated in the plasma-generating space 15 is formed from thepartition plate 14, upper vessel 12 a and plate-shaped electrode(high-frequency electrode) 20 which are arranged in an approximatelycentral position.

[0048] A plurality of holes 20 a are formed in the electrodes 20. Theelectrodes 20 are supported and fixed by means of two insulator parts 21a, 21 b which are installed along the inner face of the side part of theupper vessel 12 a.

[0049] An is to be noted that the electrically conductive element 32 issandwiched between the partition plate 14 and the fixing part 22, whichis made of electrically conductive material and which is positionedinside the vacuum vessel 12. The partition plate is fixed to the thefixing part 22 by means of a mounting screw 33 (FIG. 3(a)). Theelectrically conductive element 32 is a cord-shaped electricallyconductive element which has spring properties in the manner of what isreferred to as a spiral shield, and it ensures electric contact betweenthe partition plate 14 and the fixing part at ground potential andabsolutely noleakage to the film-processing space of high frequencywaves. However, provided that the partition plate 14 is mounted in sucha way that it is reliably kept at ground potential when the CVD deviceis being cleaned, it is not restricted to the structure in FIG. 3(a).

[0050] In addition, the heater 30 for heating the interior partitionplate 14 can be accommodated in the partition plate 14 as shown in FIG.3(b). In this case, a feed pipe 28 is arranged above the heater 30.

[0051] In cases in which fluoride gas is used as the cleaning gas, theheater 30 is placed in such a way that the partition plate 14 is heatedup to at least the necessary temperature, at which adsorption of thecleaning gas into the inner circumferential face of the plurality ofthrough-holes 25 provided in the partition plate 14 and the surface ofthe partition plate is prevented, said heating being carried out inaccordance with the type or types of fluoride gas. In this respect, thenumber of heaters 30 accommodated, and the state in which they arearranged, can be freely determined in accordance with the size of thepartition plate 14 and the necessary parameters of the heatingtemperature, and the like. In addition, it is possible to accommodate inthe partition plate 14, in the same way as the heater 30, a thermocoupledetection sensor (not shown in the figure) or the like for detecting theheating temperature of the partition plate 14.

[0052] Provided that the structure and heating means and the like forheating the partition plate 14 are configured so as to fulfill the aboveobjective, they are not restricted to the form shown in FIG. 3(b).

[0053] Feed pipes 23 a, 23 b, which introduce oxygen gas and cleaninggas into the plasma-generating space 15 from the outside, are installedin an insulator part 21 a. The oxygen gas feed pipe 23 a and cleaninggas feed pipe 23 b are connected to an oxygen gas supply and cleaninggas supply (neither shown in the figure) through a mass flow controllerswhich controls the flow.

[0054] A fluoride gas such as NF3, F2, SF6, CF4, C2, F6, C3F8 can beused as the cleaning gas.

[0055] In cases in which the etch rate of the cleaning gas when etchingsilicon oxide film is low, it is possible to add to the cleaning gas aninert gas such as He, Ne, Ar, Kr or Xe which is intended to increase theradical density by further raising the dissociation rate of the cleaninggas as a result of the rise of electron temperature of the plasma.

[0056] As the method introducing these additive gases, it is possible tocontinuously introduce these additive gases from oxygen gas feed pipe 23a, or from the gas feed pipe midway connected to the cleaning gas pipe23 b, or newly installed independent feed gas pipe exclusively providedfor the additive gases.

[0057] In the interior of the vacuum vessel 12, the plasma-generatingspace 15 is separated from the film-deposition processing space 16 bythe partition plate 14. However, a plurality of through-holes 25, whichfulfil specific conditions, are formed in the partition plate 14 so asto penetrate the interior space 24. The plasma-generating space 15 andthe film-deposition processing space 16 communicate only via thethrough-holes 25.

[0058] Furthermore, a plurality of diffusion holes 26 which supplymaterial in gas form to the film-processing space 16 are formed in thelower wall of the partition plate 14.

[0059] In order to prevent the material in gas form fed into thefilm-deposition processing space 16 from diffusing back to theplasma-generating space 15 side, the above_mentioned through-holes 25are formed so as to fulfill the condition uL/D>1 where the gas flowvelocity inside the through-holes 25 is u, the effective length of thesethrough-holes 25 is L and the coefficient of mutual gas diffusion (thecoefficient of mutual gas diffusion of two types of gas on the two sidesof the through-holes 25) is D. If said conditions which are applied tothrough-holes 25 is applied, to the diffusion-holes, @ it moreeffectively prevents the active species from diffusing back to theinterior space 24 of the partition plate 14.

[0060] A feed pipe 28 for introducing material in gas form is connectedto the interior space 24. The feed pipe 28 is arranged so as to beconnected from the outside. In addition, in order to ensure that thematerial in gas form is supplied uniformly from the diffusion holes 26,a homogenizing plate 27, which has a plurality of holes perforatedtherein, is installed approximately horizontally in the middle of theinterior space 24.

[0061] An electric power feed rod 29, which is connected to theelectrodes 20, is installed in a ceiling part of the upper vessel 12 a.High-frequency electric power to be discharged to the electrodes 20 issupplied by the electric power feed rod 29. The electrodes 20 canfunction as high-frequency electrode.

[0062] The electric power feed rod 29 is covered by an insulator 31, andinsulation from other metal surface can be.

[0063] In the CVD system according to the embodiment shown in FIG. 2 thestructure of the electrodes is modified in comparison with theembodiment shown in FIG. 1, and the high-frequency electrode 20 areinstalled in a position on the upper side of the plasma-generating space15, plasma electric discharges being generated between thehigh-frequency electrodes 20 and the partition plate 14.

[0064] The basic structural elements are essentially the same as thestructural elements of the CVD system according to the embodimentpresented in FIG. 1 and identical reference symbols have been used forcommon structural elements, hence there will not be repetition of thedetailed description here.

[0065] A characteristic configuration of the embodiment shown in FIG. 2is provided with an insulator part 21 a on the inner side of the ceilingpart of the upper vessel 12 a, and the electrodes 20 are arranged on theunderside of said insulator part 21 a. There are no holes 20 a formed inthe electrodes 20 so that it has the shape of a single plate. Theplasma-generating space 15 is formed by the electrodes 20 and partitionplate 14, which forms a parallel plate type electrode configuration.

[0066] The rest of the configuration is essentially the same as theconfiguration of the first embodiment.

[0067] A general description will be given of the film-deposition methodwhich uses a cleaning method according to the invention, with respect tothe CVD system configured as above. A glass substrate 11 is transferredto the interior of the vacuum vessel 12 by means of a transferring robot(not shown in the figure), and is placed on the substrate-holdingmechanism 17. The interior of the vacuum vessel 12 is exhausted by meansof the exhaust device 13, and a prescribed vacuum state is maintained byreducing the pressure. Next, oxygen gas is fed into theplasma-generating space 15 of the vacuum vessel 12 through the oxygengas feed pipe 23 a.

[0068] A material in gas form, for example silane, is fed into theinterior space 24 of the partition plate 14 through the feed pipe 28.The silane is fed firstly into the upper side part of the interior space24, it is homogenized by the homogenizing plates 27 and moved to thelower side part, and next fed directly into the film-depositionprocessing space 16 through the diffusion holes 26, i.e., without cominginto contact with the plasma. The substrate-holding mechanism 17 whichis installed in the film-deposition processing space 16 is maintained inadvance at a prescribed temperature because electricity is transmittedto the heater 18.

[0069] In the state mentioned above, high-frequency electric power issupplied to the electrodes 20 via the electric power feed rod 29.Electric discharge is produced by means of this high-frequency electricpower, and oxygen plasma 19 is generated in the vicinity of theelectrode 20 inside the plasma-generating space 15. By virtue of thefact that oxygen plasma 19 is generated, radicals (excited activespecies ) which are neutral excited species are generate d, siliconoxides are deposited on the surface of the substrate 11.

[0070] Next, a description will be given of a cleaning method accordingto the invention which is applied to the above_mentioned CVD system, forthe case in which NF3 gas is used as the cleaning gas.

[0071] Cleaning is performed periodically at every preset time intervalor when a preset number of substrates are processed. For cleaning, afterstopping of a material gas feeding such as silane gas, and by replacingthe oxygen gas which is introduced into the plasma generation space atfilm deposition period with fluorine gas. System configuration is notdifferent by almost same even if used cleaning gase differs.

[0072] A partition plate 14 which is formed from electrically conductivematerial is placed at ground potential, NF3 gas as cleaning gas is fedinto the plasma-generating space 15, and fluorine radicals are generatedinside the plasma-generating space 15 by supplying high-frequencyelectric power to the electrodes 20. The fluorine radicals which aregenerated are fed into the film-deposition processing space 16 throughthe plurality of through-holes 25 in the partition plate 14, and by thismeans the interior of the film-deposition processing space 16 iscleaned.

[0073] It is also possible to admix an inert gas, such as Ar gas, oroxygen gas to the cleaning gas (NF3) in order to improve the cleaningspeed.

[0074] In addition, oxygen can be used as the cleaning gas in caseswhere carbonates are deposited.

[0075] In addition, in cases where fluoride gas is used as the cleaninggas, the adsorption of fluorine onto the inner circumferential face ofthe through-holes 25 and the surface of the partition plate must beprevented, and depending on the type of fluoride gas used as thecleaning gas, it is desirable to heat the partition plate 14 to 200° C.or more by means of the heater 30, when fluorocarbon gas such as CF4,C2F6, C3F8 or nitrogen fluoride gas such as NF3 are used, for example.Or, it is desirable to heat the substrate 14 to a temperature of 100° C.or more in cases when using flurosulfur gas such as SF6, while carryingout said cleaning process.

[0076] An example of specific setting values for the cleaning method fora silicon oxide film according to the present invention is given below.

[0077] Ar gas for speeding up the dissociation of cleaning gas wasadmixed to the cleaning gas (NF3 ) with an Ar gas flow rate of 100cm3/min (0.18 g/min) under standard conditions with a power applied tothe 60 MHz high-frequency electrodes 20 of 2kW, and a mass flow rate,under standard conditions, of the NF3 cleaning gas of 200 cm3/min (0.63g/min). The pressure of the film-deposition processing space 16 was 16Pa. The speed with which the silicon oxide in the film-depositionprocessing space 16 was removed, in other words the cleaning speed, was30 to 40 nm /min.

[0078] As has been made clear in the description above, by means of thepresent invention, it is possible to provide an optimum cleaning methodfor a system which can deposit silicon oxide film and the like on alarge-area substrate using a material in gas form such as silane bymeans of plasma CVD, in which CVD system, for example, the interior ofthe vacuum vessel is divided into a plasma-generating space and afilm-deposition processing space by the position of an electricallyconductive partition plate with a plurality of through-holes ordiffusion holes formed therein, and active species are generated in theplasma-generating space and are fed into the film-deposition processingspace through a plurality of holes in said partition plate.

[0079] With the cleaning method according to the present invention, byperforming optimum cleaning after film-deposition, the generation ofparticles can be reduced and the CVD system of the present formconfiguration can be used efficiently in the manufacture of large-areasubstrates without interpret due to exposing the interior of thedepositing chamber to the atmospheric ambient for cleaning, and yetthere is no product contamination due to fluorines caused by thecleaning gas, and it is possible to operate continuously in a stabilizedfashion without interpret due to exposing the interior of the depositingchamber to the atmospheric ambient for cleaning, which results in a highyield.

[0080] Although only preferred embodiments are specifically illustratedand described herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting from the spirit and intended scope of the invention.

In the claims
 1. A method of cleaning a CVD vacuum vessel which has anelectrically conductive partition plate which divides an interior of thevacuum vessel into a plasma generating space and a film-depositionprocessing space, and in the electrically conductive partition platethere is a plurality of through-holes connecting the plasma generatingspace to the film-deposition processing space, the method comprising thesteps of: feeding a cleaning gas into the plasma-generating space;generating active seeds by applying high-frequency electric power toelectrodes arranged in the plasma-generating space; feeding thegenerated active species into the film-deposition processing spacethrough the plurality of through-holes in the electrically conductivepartition plate; and cleaning the film-deposition processing space bythe active seeds which have been fed into this film-depositionprocessing space.
 2. The method of claim 1, further comprising the stepof maintaining the electrically conductive partition plate at groundpotential.
 3. The method of claim 1, further comprising the step ofheating said electrically conductive partition plate.
 4. The method ofclaim 1, wherein the cleaning gas is one or more types of fluoride gas.5. The method of claim 4, wherein the fluoride gases are NF3, F2, SF6,CF4, C2F6 and C3F8.
 6. The method of claim 1, further comprising thestep of adding oxygen gas to the cleaning gas.
 7. The method of claim 6,wherein an amount of oxygen gas added is such that the concentration is60% or less.
 8. The method of claim 1, wherein the cleaning gas is O2.9. The method of claim 1, further comprising the step of adding any ofHe, Ne, Ar, Kr and Xe to the cleaning gas.
 10. The method of claim 3,wherein the heating of said electrically conductive partition plate iscarried out within a temperature range which inhibits the adsorption offluorine onto an inner circumferential face of the through-holes and thesurface of the partition plate.
 11. The method of claim 10, wherein thecleaning gas is carbon fluoride gas or nitrogen fluoride and theelectrically conductive partition plate is heated to 200° C. or more.12. The method of claim 10, wherein the cleaning gas is sulfur fluoridegas and the electrically conductive partition plate is heated to 100° C.or more.
 13. A method of cleaning a CVD system in which active bygenerating plasma inside a vacuum vessel and film is deposited on asubstrate accommodated in the vacuum vessel by the active species andmaterial in gas form, wherein said CVD system is configured in such away that, by providing said vacuum vessel with an electricallyconductive partition plate, the interior of said vacuum vessel isdivided into two chambers by said electrically conductive partitionplate, and in the interior of one of said two chambers into which theinterior of the vacuum vessel is divided, a plasma generating space inwhich high frequency electrode is arranged is formed, and in theinterior of the other chamber a film-deposition processing space inwhich there is arranged a substrate-holding mechanism on which saidsubstrate is mounted is formed, said CVD system is configured in such away that in said electrically conductive partition plate there is aplurality of through-holes made to pass through said plasma-generatingspace and said film-deposition processing space, the plurality ofthrough-holes are formed in such a way that where the velocity of gasflow inside said through-holes is U, the effective length of thethrough-holes is L and the coefficient of mutual gas diffusion is D, thefollowing condition uL/D>1 is fulfilled, and an interior space is formedtherein which is divided off from said plasma-forming space and whichcommunicates with said film-deposition processing space via a pluralityof diffusion holes, and said material in gas form is supplied to theinterior space of said electrically conductive partition plate from theoutside and fed into said film-deposition processing space through saidplurality of diffusion holes, and said CVD system introduces into saidfilm-deposition processing space, through the plurality of through-holesformed in said partition plate, said active species which are generatedin said plasma-generating space by applying high-frequency electricpower to said high-frequency electrodes and thus producing a plasmaelectric discharge in said plasma-generating space, the cleaning methodcomprising the steps of: maintaining the electrically conductivepartition plate at ground potential; feeding a cleaning gas into theplasma-generating space; generating active seeds by applyinghigh-frequency electric power to electrodes arranged in theplasma-generating space; feeding the generated active seeds into thefilm-deposition processing space through the plurality of through-holesin the electrically conductive partition plate; and cleaning thefilm-deposition processing space by the active species which are fedinto this film-deposition processing space.
 14. The method of claim 13,further comprising the step of heating said electrically conductivepartition plate.
 15. The method of claim 13, wherein the cleaning gas isone or more types of fluoride gas.
 16. The method of claim 15, whereinthe fluoride gases are NF3, F2, SF6, CF4, C2F6 and C3F8.
 17. The methodof claim 13, further comprising the step of adding oxygen gas to thecleaning gas.
 18. The method of claim 17, wherein an amount of oxygengas added is such that the concentration is 60% or less.
 19. The methodof claim 13, wherein the cleaning gas is O2.
 20. The method of claim 13,further comprising the step of adding an y of He, Ne, Ar, Kr and Xe tothe cleaning gas.
 21. The method of claim 13, wherein the heating ofsaid electrically conductive partition plate is carried out within atemperature range which inhibits the adsorption of fluorine onto_theinner circumferential face of said through-holes and the surface of thepartition plate.
 22. The method of claim 21, wherein the cleaning gas iscarbon fluoride gas or nitrogen fluoride and the electrically conductivepartition plate is heated to 200° C. or more.